1. Field of the Invention
The present invention relates to a rear projection type screen used in a rear projection television or the like, and in particular to a front faceplate used in the rear projection type screen.
2. Description of the Prior Art
A rear projection type screen used in a rear projection television or the like generally has a configuration in which two lens sheets are placed on top of one another. Specifically, a Fresnel lens sheet that narrows image light from a CRT or image light that has passed through liquid crystals so as to make the image light be within a certain angular range is placed on the light source side, and a lenticular lens sheet that has a function of spreading out the image light that has passed through the Fresnel lens sheet into a suitable angular range is placed on the observer side.
A schematic perspective view of a rear projection type screen is shown in FIG. 6. As shown in FIG. 6, the rear projection type screen is basically composed of a front faceplate 1, a lenticular lens sheet 2 and a Fresnel lens sheet 3. There are disclosures concerning the front faceplate 1 in, for example, Japanese Patent Application Laid-open No. H08-22077 and Japanese Patent Application Laid-open No. H07-307912. The front faceplate 1 is provided for purposes such as protecting the lenticular lens sheet and obtaining a surface glossiness similar to that of a normal cathode ray tube type television.
Lenticular lenses 21 are provided on the surface of the lenticular lens sheet 2 from which the image light enters (hereinafter referred to as the xe2x80x98light-entering surfacexe2x80x99). Of the surface of the lenticular lens sheet 2 from which the image light exits (hereinafter referred to as the xe2x80x98light-exiting surfacexe2x80x99), convergence parts 22 where light from the lenticular lenses 21 formed on the light-entering surface of the lenticular lens sheet 2 is converged are generally formed in convex lens shapes. Non-convergence parts 23 where light from the lenticular lenses 21 formed on the light-entering surface of the lenticular lens sheet 2 does not converge (i.e. parts other than the convergence parts 22) are made to have a projecting shape with a summit portion thereof parallel to the lenticular lens sheet 2. An external light absorbing layer 24 comprising a black coating or the like is provided on the summit portion of each projecting part and on the portions of the side surfaces of each projecting part close to the summit portion (i.e. the upper portions of the side surfaces), thus forming external light absorbing parts 25.
A method of improving color shift and visual field angle in such a rear projection type screen is proposed in Japanese Patent Application Laid-open No. H07-248537. Disclosed in that document are a lenticular lens sheet not containing a diffusing agent, and a front faceplate for which the surface thereof on the light-exiting side (i.e. the side of the observer) is made to be a mirror surface and which has a diffusing layer containing a diffusing agent on the light-entering surface thereof on the side of the lenticular lens sheet. FIG. 7 shows a sectional view of such a conventional rear projection type screen. As shown in FIG. 7, there is a diffusing layer containing a diffusing agent 4 on the light-entering surface of the front faceplate 1.
In the case of a rear projection type screen having the structure disclosed in the above document, a wrinkly shape, i.e. a roughness consisting of small undulations, occurs on the light-entering surface of the front faceplate due to the influence of the diffusing agent, leading to the problem of an increase in reflection of external light and hence a reduction in contrast.
In the case of the conventional art, there is thus a problem that, if a diffusing layer is provided on the light-entering surface of the front faceplate to improve the color shift and the visual field angle, then the contrast is reduced.
In view of the foregoing, it is an object of the present invention to provide a front faceplate used in a rear projection type screen and a front-faceplate-equipped lenticular lens sheet, for which color shift and visual field angle are improved with no reduction in contrast.
It is another object of the present invention to provide a rear projection type screen for which color shift and visual field angle are improved with no reduction in contrast.
According to one aspect of the present invention, for achieving the above-mentioned object, there is provided a front faceplate used in a rear projection type screen, which have a diffusing layer in a region prescribed distances away from each of a light-entering surface and a light-exiting surface of the front faceplate.
Consequently, color shift and visual field angle are improved with no reduction in contrast.
Also, the lenticular lens sheet is bonded to the front faceplate at summit portions of projecting external light absorbing parts of the lenticular lens sheet. Consequently, a part of the external light is absorbed at the bonding portion, resulting in it being possible to improve the external light contrast.
According to another aspect of the present invention, there is provided a rear projection type screen, comprising the above mentioned front faceplate, a lenticular lens sheet that is bonded to the front faceplate at summit portions of projecting external light absorbing parts of the lenticular lens sheet, and a Fresnel lens sheet positioned on the side of the surface of the lenticular lens sheet opposite to the surface of the lenticular lens sheet bonded to the front faceplate.
Consequently, color shift and visual field angle are improved with no reduction in contrast.
The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for purpose of illustration only and are not intended as a definition of the limits of the invention.